http://arxiv.org/abs/1711.05494
In the work, we adopt a model-dependent method to investigate the spectral evolution for a sample of low-synchrotron-peaked (LSP) blazars composed primarily by Flat-Spectrum Radio Quasars (FSRQs), which is an important subclass of Blazars. With respect to previous works, we introduce a near-equipartition log-parabola (NELP) model to fit the quasi-simultaneous multi-waveband spectral energy distributions (SEDs), and Markov Chain Monte Carlo (MCMC) fitting procedure is employed in order to determine the best values of spectral parameters and its errors. By using the model, we not only investigate correlation between the synchrotron peak luminosity $L_{pk}^$ and its peak frequency $\nu_{pk}^$, but also investigate a new correlation of the SSC-dominant factor $\xi_s$ and $\nu_{pk}^$, and discuss its implications as to the spectral evolution. The statistical analysis and the comparison with theoretical approximation indicate that the spectral evolution in $L_{pk}^-\nu_{pk}^$ plane may be not only ascribed to variation of the characteristic energy $\gamma_{br}^\prime$ of the employed electron energy distribution (EED) but that other quantities must be varying as well. It is consistent with the previous results from the spectral analysis, and furthermore our results show that for the spectral evolution in $\xi_s-\nu_{pk}^$ plane the magnetic field $B^\prime$ may play the dominant role, and $\gamma_{br}^\prime$ may be considered to be the subdominant role. Variations of the beaming factor $\delta_b$ may be mainly responsible for the absence of a possible correlation, since $B^\prime$ is strongly anti-correlated with $R_b^\prime$. The relation is according with that derived from the analytical theory, and should be self-consistent with the underling acceleration mechanism of the employed EED.
W. Hu, B. Dai and W. Zeng
Thu, 16 Nov 17
2/55
Comments: 24 pages, 26 figures and 2 tables